Surface quality is the most crucial factor affecting the product lifespan and performance of any component. Most earlier technologies display accuracy in the micrometre or submicrometre range, surface roughness in the nanometre range, and almost no surface defects in the production of optical, mechanical and electronic parts. Such finishing methods incorporate a magnetic field to control the finishing forces using magnetorheological fluid as the polishing medium. Magnetorheological fluid (MR) consists of ferromagnetic and abrasive particles. It is a type of modern intelligent fluid. An optimum selection of magnetorheological fluid constituents and their volume concentration plays an essential role for the ultra-fine finishing of newly developed engineering products. Rheological characteristics of magnetorheological fluid can change rapidly and effortlessly with the support of an activated magnetic field. Traditional finishing methods are comparatively inferior in finishing complex freeform surfaces, due to the lack of controlling finishing forces and limitations of polishing tool movement over the complex freeform contour of the components. There are different types of processes based on the magnetorheological fluid including magnetorheological finishing, magnetorheological abrasive flow finishing, rotational magnetorheological abrasive flow finishing and ball end magnetorheological finishing. This article discusses the development of different types of magnetorheological-fluid-based finishing processes and their modes of operation. The MR fluid devices developed in the last decade are thoroughly reviewed for their working principles, characteristics and applications. This article also highlights the study of rheological characterization of magnetorheological fluid and its applications in different polishing methods appropriate for finishing various complex freeform components.
Nowadays, the surface quality of the material is crucial for industry and science. With the development of micro-electronics and optics, the demand for surface quality has become more and more rigorous, making optical surface polishing more and more critical. Plasma polishing technology is conceived as an essential tool for removing surface and subsurface damages from traditional polishing processes. The plasma processing technology is based on plasma chemical reactions and removes atomic-level materials. Plasma polishing can easily nano-finish hard-brittle materials such as ceramics, glass, crystal, fused silica, quartz, Safire, etc. The optical substrate with micro-level and nano-level surface roughness precision is in demand with the advancement in optics fabrication. The mechanical properties of super-finished optics materials are being used to fulfill the requirement of modern optics. This article discusses the processing of different types of freeform, complex and aspheric optical materials by the plasma polishing process used mainly by the optical industry. The plasma polishing devices developed in the last decade are thoroughly reviewed for their working principles, characteristics and applications. This article also examines the impact of various process parameters such as discharge power, rate of gas flow, mixed gas flow ratio and pressure on the plasma polishing process.
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